Suspensions for suspending sliders in hard disk drives are well known in the art. Referring to FIG. 1, in a typical hard disk drive, the drive's read/write head 10 is included in, or mounted to, a slider 12, which has an aerodynamic design and is supported by a suspension 14. The slider's aerodynamic design allows for airflow between the slider and the disk drive's spinning disk 16. This airflow generates lift, which allows the read/write head to fly above the spinning disk's surface an optimal distance for reading data from, or writing data to, the disk. A typical suspension includes a flexure (not shown), a load beam 20, and a baseplate 22. The slider is bonded to the flexure, also referred to as a gimbal, which permits the slider to pitch and roll as it tracks fluctuations in the surface 24 of the disk.
The flexure (not shown) is coupled to a distal end 26 of the load beam 20, which typically is formed from a flat sheet metal, e.g., stainless steel foil, and includes a spring portion 28 that applies a loading force, also known as a “pre-load” or “gram force,” to the slider 12. The pre-load force counteracts the lift that is generated by the interaction between the slider and the spinning disk 16, and brings the slider into a predetermined close spacing to the disk surface 24 while the disk is spinning. The desired pre-load force is achieved by forming one or more bends 30 in the spring portion of the load beam, taking into account the spring constant of the load beam's material, its mass, and the expected load. A proximal end 32 of the load beam is coupled to the baseplate 22, which is configured to couple to an actuator arm 34. The actuator arm moves under motor control to precisely position the slider, and thus, the drive's read/write head 10 relative to the disk surface.
Referring additionally to the views of an example load beam 20 shown in FIGS. 2A-C, the load beam's distal end 26 is generally a rigid structure having its edge regions 36 formed into rails 38 to increase its rigidity. As shown in FIG. 2A, the load beam has a generally triangular shape 40 that is referred to as a double-delta configuration, which includes a first trapezoidal region 42 that is coupled to a second trapezoidal region 44. The rails run the length of both sides 46 of the load beam's first and second trapezoidal regions, and the rails are bent at the points 48 where the first and second trapezoidal regions meet.
During manufacturing, the load beam 20 is cut or etched from a flat sheet of metal forming the example shape 50 shown in FIG. 2B. After the outline of the load beam is cut from the flat sheet of metal, the rails 38 are formed by folding up the edge regions 36 on both sides 46 of the load beam. For reference, fold lines 52 are shown in FIG. 2B. Typically, both of the rails are folded in the same direction perpendicular to the rest of the load beam, i.e., the first and second trapezoidal regions 42 and 44, respectively.
In the case of a double-delta configured load beam 20 having continuous unbroken rails 38 across the intersection of the first and second trapezoidal regions 42 and 44, respectively, the load beam can have a drooped shape 54 after the rails are formed, i.e., folded. Referring additionally to FIG. 2C, the droop, also referred to as unwanted sag, results from the bend 56 at point 48 in each of the rails and can be quantified as the angle θ formed between the plane 58 in which the first trapezoidal region lies, i.e., the first plane, and the plane 60 in which the second trapezoidal region lies, i.e., the second plane. This droop naturally results when the rails are folded because of the limited length of material that makes up the load beam's edge regions 36.
Preferably, a load beam's distal end 26 is a generally planar structure without droop 54. Because of manufacturing variability, the droop, i.e., the angle θ between the first plane 58 and the second plane 60, for double-delta configured load beams 20 can vary. This variation in droop can result in a corresponding variation in the pre-load for the slider 12, which, in turn, affects the disk drive's read/write performance. When a load beam has a double-delta configuration, droop can be reduced by breaking the continuum of the rails 38 by forming a gap (not shown) in each of the rails where the first and second trapezoidal regions 42 and 44, respectively, meet. However, adding this gap lessens the rigidity of the load beam, causing the load beam to offer less resistance to bending than if the rail was continuous. Alternatively, after the rails are formed, the load beam could be subjected to a secondary bending operation that would reverse the droop, that is, overbend the load beam in a direction opposite to the direction of the droop to correct the overall shape of the load beam back into a generally planar shape. However, this secondary bending operation can add additional variability to the value of the load beam's pre-load.
It should, therefore, be appreciated that there is a need for an efficient method for forming a relatively planar double-delta configuration load beam 20 having rails 38 without having to form a gap in each of the rails before bending the rails into position, and without having to reverse bend the load beam to reverse any droop 54 in the load beam. The present invention satisfies these needs.